1. Field of the Invention
The present invention relates to an apparatus for assembling a piston in a swash plate-type compressor which automatically assembles the piston to enhance performance and productivity of the compressor.
2. Background of the Related Art
A compressor in an air conditioning system for a vehicle selectively receives, via engagement/disengagement of an electromagnetic clutch, power of an engine transmitted through a pulley of a vehicle. The compressor inhales refrigerant, which is heat exchanged in an evaporator, compresses the refrigerant through a linear reciprocating motion, and then dispenses the compressed refrigerant to a condenser.
Such compressors are of various types, which are generally divided into reciprocating and rotary compressors according to compressing methods and structures. The reciprocating compressors include in particular a crank, swash plate and wobble plate type compressors. The rotary compressors include vein rotary and scroll type compressors. These compressors also include a variable capacity compressor which can vary its compressing capacity.
A prior art of the variable capacity compressor is disclosed in Japanese Patent Application Laid-Open No. 2001-3859.
Herein, description will be made about an assembling apparatus related to the present invention instead of the entire structure of a swash plate type compressor having variable capacity.
As shown in FIG. 1, a driving shaft 16 is supported by a driving shaft supporting jig 44 in an assembly Pa including the driving shaft 16, a rotor 17, pistons 22 and a swash plate 18, and then the pistons 22 are supported by a piston supporting jig 45.
Positioning portions 43 of a positioning jig 41 are inserted into cylinder bores 33 of a cylinder block 12 so that positioning projections 43a formed at ends of the positioning portions 43 are engaged into positioning grooves 22c in the pistons 22.
Where the positioning projections 43a are engaged into the positioning grooves 22c, the cylinder block 12 moves slidingly in a direction indicated with an arrow in FIG. 2.
Then, in response to movement of the cylinder block 12, the piston-supporting jig 45 is separated from the pistons 22 so that the cylinder block 12 completely covers the pistons 22.
In the final stage, the positioning portions 43 are drawn out of the cylinder bores 33 of the cylinder block so as to complete the operation of assembling the pistons 22.
However, the foregoing prior art for assembling the compressor as above has the following problems:
First, the prior art allows the pistons 22 to be introduced into the cylinder bores 33 of the cylinder block 12 via engagement of the positioning projections 43a into the positioning grooves 22c. If the positioning grooves 22c and the positioning projections 43a are not correctly formed, respectively, in the pistons 22 and the positioning portions 43, it is impossible to engage the positioning projections 43a into the positioning grooves 22c and thus to assemble the pistons into the bores.
As a result, it is required to precisely form the positioning projections and the positioning grooves which enable the above-mentioned assembling operation. In particular, it is difficult to form the positioning grooves in piston bodies and the forming cost is excessive.
Second, after forming the positioning grooves and the positioning projections, an additional operation is needed to test whether the grooves and the projections are formed in correct positions.
Third, because the operation of assembling the pistons is not provided with a separate greasing device, the pistons are not easily assembled into the cylinder bores of the cylinder block.
Fourth, since the positioning grooves are directly formed in the piston bodies, endurance and compressibility of the pistons are remarkably degraded thereby deteriorating performance of the compressor.